Core structure for transformers



V. E. ALDEN.

CORE STRUCTURE FOR TRANSFORMERS.

, APPLICATION FILED JULYIO, 1918- mwsza Patented Jan. 31, 1922.

6 E W 0 T/ .m W ME I M WITNESSES: W3

UNITED STATES PATENT OFFICE.

VERN E. ALDEN, OF IB ALTIMORE, MARYLAND, ASSIGNOR TO WESTINGHOUSE EIIEC-TRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

CORE STRUCTURE FOR TRANSFORMERS.

To all whom it may concern:

Be it known that I, VERN E. ALDEN, a citizen of the United States, and aresident of Baltimore, '11 the State of Maryland, have invented a newand useful Improvement in Core Structures for Transformers, of which thefollowing is a specification.

My invention relates to the construction of transformer core members andis particularly applicable to the construction of core members for largepolyphase transformers which are built up of lamination layers.

In transformers of this type in which the core member is constructed ofsuch laminated layers, the several layers are composed of punchingswhich are usually rectangular in shape and are built up around thetransformer coils after the latter have been placed in position. It hasbeen found that, when such transformers are designed for large-capacityservice, the iron losses present therein are excessive. Moreover, whentransformers attain the size necessary for large capacities, thepunchings used become quitev large and unwieldy, especially those usedto form the side portions of the transformer core member.

It is one ofthe objects of my improved form of construction to reducethe iron losses to a minimum by so constructing the lamination layersthat the flux will be uniformly distributed among the different layersof the core member. To the end of attaining this object, I so proportionand arrange the air gaps between the various punchings forming a part ofeach layer, that the magnetic reluctance of all paths in parallel shallbe substantially uniform, and also so arrange said punchings that thereshall be no tendency for the magnetic flux to concentrate in any onelayer of said transformer core member and thereby cause eX- cessiveheating in said layer.

Another object of my invention is to construct a laminated-layertransformer core member which shall make use of smaller punchings thanhas heretofore been possible and thereby greatly reduce the cost ofconstruction, since those punchings which are now discarded as too smallfor use in the larger transformers will then be used. Moreover, by theuse of smaller punchings in the construction of laminated layers, thelabor incident to the handling and placing coils.

1918. Serial No. 244,307.

in position of the large punchings will be greatly minimized.

The difliculties encountered in the present type of construction and themanner in which I propose to overcome said difliculties will be morereadily understood by reference to the accompanying drawings in whichFig. 1 is a sectional view taken on the, line II of Fig. 2, both of saidfigures showing the manner in which the laminations are placed in acore-type transformer; Fig. 3 is a sectional view of a shell-typetransformer, and Fig. 4.- is an elevational view of a portion of thetransformer shown in Fig. 3.

Referring more particularly to Fig. 1, a transformer, comprising a core1 and coil sections 2, 3 and 4, consisting of primary and secondarywindings which embrace different leg portions of the core, are shown. Itwill be understood that the lamination layers are placed one on top ofanother to provide the built-up core member for such a transformer andit will be further observed that, in this figure, the type oftransformer commonly known as the core type is shown.

Referring now more specifically to the exact form of construction of theindividual lamination layers, it will be observed that the middleportionof the core is composed of long punchings 5 so alternated thatthe ends project first at one side of the coils and then at the other.In the layer shown, short punchings 6 and 7 are located at one side ofthe coils in end-to-end engagement with each other and with their outerends in respective engagement with the side edges of the outer legpunchings 8 and 9. At the other end of the core, punchings 10 and 11have side-edge engagement with ends of the punchings 8 and 9 and endengagement with the side edges of the projecting end of the punching 5.,hen the next succeeding layer is placed on top of the one here shown,the manner of building the said layer is exactly-reversed, the punchings10 and 11 and 6 and 7 of one layer being placed on top of the punchings6 and 7 and 10 and 11 of the next adjacent layer, respectively, and thepunchings 5,, -8 and 9 being reversed and so placed as to projectoppositely from the The manner of building up the punchings in thewaydescribed will be more clearly understood by reference to Fig. 2, in

sult in a layer having no air gaps being long member in which it will beobserved that, at the point of abutment of the side portion of the coremember and the interior or embraced portion of the said member, two airgaps are provided in alternate layers, while one gap is inserted in thelayers which are sandwiched between said alternate layers.

In the transformer, as at present constructed, it has been usual to usea single place of the two punchings 6 and 7. I have found, however,that, by so employing two punchings instead of one, the iron losses arereduced to a minimum and the tendency for the magnetic. flux toconcentrate in any one portion of the structure is eliminatedl Referringnow toFig. 2, it is apparent that the method heretofore practised willreplaced in parallel with a layer having two gaps and this will, inturn, cause a heavy concentration of the magnetic flux in the layerhaving no air gap. It is, therefore, the purpose of my invention to sodivide the hitherto-used long member that the air gaps in adjacentlayer's'will present substantially equal magnetic reluctance to the fluxin said layers.

Moreover, I intend to so proportion the reluctance of the single gapthat but one gap need be used in the portion of the lamination layer, asshown at the top of Fig. 1. This may readily be accomplished by makingthe gap between the punchings 6 and 7 slightly larger than usual, andthe magnetic reluctance of said gap will then be equal to that presentedby the sum of the reluctancesof the gaps between the long member. 5 andthe two punchings 10 and 11.

In Fig. 3, I have shownthe construction I propose to use in a shell-typetransformer. It will be observed that the coils in the shelltypetransformer are embraced by the core member and it is, therefore, quitean advantage to be able to use the smaller punchings'in building up theinterior portion of such a core member, especially in view of the factthat, for some of the large high voltage, three-phase, shell-typetransformers, it

. is not possible to cut the long punchings from the ordinary sheets ofcommercial sheet steel.

Here again, it will be observed that, infi stead of a slngle long memberbridging I across, and abutting against, the interior punching, Iha-veused two members and have'so placedthesingle air gap between thesetwo members that amagn'etic reluctance equal to that interposed in theadjacent-"layer by the particular form thereof, is inserted in thelamination layer shown.

- Fig. 4 shows themanner in which the lamination layers are piled toform a core member for a transformer of the shell type in order toaccomplish the purpose of my invention. x

lVhile I have shown the long member heretofore used as subdivided at'themiddle of the zone of abutment to the interiorl-y extending member, itwill be apparent that the air gap may be placed anywhere in this regionso long as the reluctance of said gap is equal to the reluctance of twogaps of the layers immediately adjacent thereto and I, therefore, wishno further limitation to be placed on the structure shown herein than isimposed by the prior art or by the scope of the appended claims.

I claim as my invention:

1. In a transformer, the combination with a primary and a secondarycoil, of a core structure comprising three legs and interconnecting sideportions operatively associated with said coils, said core structurebeing built up of lamination layers, alternate layers of said sideportions being provided with oneabutment joint and the remainder legsand the remainder of said layers being provided with one transverse airgap at the point of abutment with said core leg.

3. In a transformer, the combination with a primary and a secondarycoil, of a core structure comprising three legs and interconnecting sideportions operatively asso-' ciated with said coils, said core structurebeing built up of lamination layers, alternate layers of said sideportions being provlded with two transverse air gaps at the point ofabutment with one of said core legs and the remainder of said layersbeing provided with one transverse air gap at the point of abutment withsaid core leg, the reluctance of-the air gap of said last mentioned setof layers being substantially equal to that of the two air gaps in saidrst mentioned set of layers.

4. In a transformer, the combination with a primary and a secondarycoil, of a core structure comprising a centrally disposed core legandtwo side members operatively associated with said coils, said corestructures'being built up of lamination layers,

certain ofsaid layers having the lamina- .tions of said centrallydisposed core leg extending intermediate two spaced portions of sidemembers and the remainder of said layers having an air gapprovidedbetween two abutting portions of side members.

5. In a transformer, the combination with a primary and a secondarycoil, of a core structure comprising a centrally disposed core leg andtwo side members operatively associated with said coils, said corestructures being built up of lamination layers,

alternate of said layers of laminations having a portion of thecentrally disposed core leg disposed intermediate two spaced portions ofside members and forming two air gaps therein and the remainder of saidlayers of laminations being provided with an air gap of a magneticreluctance equal 15 to that of the two air gaps of the next adjacentlayers. a

In testimony whereof, I have hereunto subscribed my name this 25th dayof June, 1918.

VERN E. ALDEN.

